More accurately described as homing switches for this application, these "limit" switches are used when resetting the machine's position. These limit switches are the type with a built in roller. This roller is positioned right on top of the actuator which is nice because it helps keep the metal strip from accidentally getting bent.
The limits should be wired as normally open when used with the Sun Harvester Shield so make sure you use the leads labeled "NO" and "COM".
These limits come in sets of two, enough for one machine.